1. Field of the Invention
The present invention relates to an Optical Crossconnect (OXC) fabric for connecting an optical signal in an input fiber to an output fiber and that includes an array of I/O fibers, an array of tiltable mirrors, and a reflector.
2. Description of the Related Art
An Optical Crossconnect (OXC) device comprises an array of lenses, a corresponding array of mirrors, and a reflector. An array of I/O fibers which corresponds to the array of lenses is received in the device so that the array of mirrors corresponds to the array of I/O fibers. Each of the mirrors is tiltable about 2 axes for directing an input signal received from its corresponding I/O fiber (i.e. an input fiber) against the reflector to another mirror and to an output one of the I/O fibers, thereby signally connecting the input fiber to the output fiber and functioning as a switch.
To ensure proper positioning of the mirrors for optimizing the connection of the optical signal from the input I/O fiber to the output I/O fiber, optical taps are formed in each of the I/O fibers for monitoring the optical signals and ensuring that the output signal approximates the input signal. If a difference between the input and output signals exceeds a threshold value, the mirror positions are adjusted to optimize the output signal. A problem with this arrangement is that the optical taps direct a portion of the optical signal away from the I/O fiber. Furthermore, OXCs typically include arrays of approximately 256 fibers and mirrors. Accordingly, the optical taps add considerable cost to the OXC because they are required for each of the I/O fibers.
The present invention uses signals present in an optical translation unit to monitor the mirror position and maintain optimal performance of an optical crossconnect (OXC) device. After an optical signal is transmitted from its source to the OXC device, it is generally degraded from its original form and amplitude due to attenuation and other losses and/or disturbances that it may receive or that are present along its path. For this reason, each I/O fiber includes an optical translation unit (OTU) which detects the incoming signal and regenerates the signal to its proper intensity and form. To accomplish this task, the OTU converts the optical signal to an electrical signal, performs the regeneration on the electrical signal, and transforms the regenerated electrical signal into an optical signal for continued transmission of the optical signal to the OXC fabric. Although the OTU is not a part of the OXC fabric and is typically controlled separately therefrom, the electrical signal present in the OTU can be used instead of an optical tap connected to the optical fiber to control the mirror position, because that electrical signal in the OTU represents the optical signal that is transmitted to the OXC fabric. Since the presence of an OTU in the fibers is required to ensure signal quality, the use of the OTU for control of the mirror position reduces the number of required parts for the OXC and thereby does not significantly add to the cost of manufacture.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.